1. Field of the Invention
The present invention relates to a thermal activation device for thermally activating a heat-sensitive adhesive layer of a sheet material having a printing layer formed on one surface of a sheet-like base material and the heat-sensitive adhesive layer formed on the other surface thereof.
2. Description of the Related Art
For example, in a distribution center and shops, labels for displaying various types of information such as prices and for displaying barcodes for management by means of POS (point of sales) terminals have been used by being attached to articles. As this type of label, a proposal has been made of a label, which is issued using a sheet material having a printing layer formed on one surface of a sheet-like base material and a heat-sensitive adhesive layer formed on the other surface thereof.
In general, a label issuing instrument which issues the label having the heat-sensitive adhesive layer as described above includes a printing apparatus that prints various types of information on a thermal printing layer of the sheet material supplied from the sheet supply apparatus, a cutting apparatus that cuts the sheet material for which the printing has been performed by the printing apparatus, and a thermal activation device that thermally activates the heat-sensitive adhesive layer of the sheet material.
Moreover, as a conventional label issuing instrument including the thermal activation device, there is known a structure in which a guiding apparatus that sags and guides the sheet material is disposed between the cutting apparatus and the thermal activation device (for example, refer to JP 2003-316265 A).
The conventional thermal activation device will be briefly described with reference to the drawing.
As shown in FIG. 7, a conventional thermal activation device 110 includes: a thermal activation head 111 for thermally activating a heat-sensitive adhesive layer of a sheet material 103; a platen roller 112 which is brought into press contact with the thermal activation head 111, sandwiches the sheet material 103 between the platen roller 112 itself and the thermal activation head 111, and conveys the sheet material 103 in the conveying direction that is a direction indicated by an arrow L; a pair of feed-in rollers 113a and 113b for feeding the sheet material 103 conveyed from the cutting apparatus into the thermal activation device 110; a sheet guide portion 117 for guiding the sheet material 103 conveyed from the cutting apparatus; and a discharge roller 115 for discharging the sheet material 103 thermally activated by the thermal activation head 111 to the outside of the thermal activation device 110.
In the thermal activation device 110 as described above, an outer diameter of the platen roller 112 is set at approximately 12 mm, and outer diameters of the feed-in rollers 113a and 113b are set at approximately 8 mm. Moreover, in the sheet guide portion 117, an opposing gap d′ through which the sheet material 103 is inserted is set at approximately 0.9 mm. A distance e′ of the opposing gap d′ in the conveying direction of the sheet material 103 is set at approximately 7.8 mm. Moreover, in the thermal activation device 110, a distance f′ between an upstream-side holding position of the sheet material 103, where the sheet material 103 is held by the pair of feed-in rollers 113a and 113b, and a downstream-side holding position of the sheet material 103, where the sheet material 103 is held by the platen roller 112 and the thermal activation head 111, is set at approximately 23.1 mm.
In the thermal activation device 110 constructed as described above, the sheet material 103 fed in from the cutting apparatus side is fed in by the pair of feed-in rollers 113a and 113b, and is inserted into the opposing gap of the sheet guide portion 117. The sheet material 103 inserted into the opposing gap of the sheet guide portion 117 is further fed in by the feed-in rollers 113a and 113b, and one end thereof is thus brought into contact with a peripheral surface of the platen roller 112.
The sheet material 103 which is brought into contact with the platen roller 112, is inserted between the platen roller 112 and the thermal activation head 111 as the platen roller 112 is rotationally driven. Then, a heat-sensitive adhesive layer of the sheet material 103 inserted between the platen roller 112 and the thermal activation head 111 is thermally activated by the thermal activation head 111, and the sheet material 103 is conveyed toward the discharge roller 115 by friction force between the sheet material 103 itself and the peripheral surface of the platen roller 112, and is discharged to the outside of the thermal activation device 110 by the discharge roller 115.
Incidentally the label issued from the sheet material having the heat-sensitive adhesive layer is sometimes used in such a manner that the entire surface of the heat-sensitive adhesive layer is not thermally activated evenly, but only a part thereof is thermally activated to form an adhesive region, and the other portions are left as a non-adhesive region which is not thermally activated.
In such a label, for example, one end side as the adhesive region of the label is attached to an article and the other end side as the non-adhesive region is not attached to the article. Moreover, in the label, for example, a tear-off line or the like is provided on a border between the adhesive region and the non-adhesive region, and in a distribution process of such articles, the other end side of the label is cut off and used as a slip for management.
As described above, in the conventional thermal activation device, when the heat-sensitive adhesive layer of the sheet material is thermally activated partially in the width direction perpendicular to the conveying direction of the sheet material, the adhesive region thermally activated by a thermal activation head and the non-adhesive region which is not thermally activated are unevenly present in the width direction of the sheet material.
In the conventional thermal activation device, a heat-sensitive adhesive layer of a sheet material held between a thermal activation head and a platen roller is thermally activated partially at a thermal activation position of the thermal activation head.
For example, with respect to a centerline in a direction of a width which is perpendicular to the conveying direction of the sheet material, in a case where a region from the centerline to one end side is activated and a region from the centerline to the other end side is not activated, with respect to the centerline of the sheet material in the width direction, a friction coefficient between the sheet material and the thermal activation head differs between the adhesive region and the non-adhesive region.
Therefore, the sheet material has a problem in that slippage occurs between the sheet material itself and the platen roller in the non-adhesive region. As a result, the sheet material is conveyed less in the non-adhesive region than in the adhesive region, and a difference occurs in conveying speed by the platen roller in the width direction. Thus, there is a problem in that the sheet material is inclined with respect to the conveying direction, thus being conveyed while skewed, thus causing skew feed.
In the sheet material conveyed while skewed as described above, while a portion thereof where the conveying speed is fast is tightly held by the platen roller and conveyed at approximately the same speed as rotation speed of the platen roller, a portion thereof where the conveying speed is slow is suspended at rest in a deflected state in the vicinity of the front portion of the platen roller. At this time, between the feed-in rollers and the plate roller, a deflection occurs in the portion where the conveying speed of the sheet material is slow. Moreover, when a trailing edge of the sheet material in the conveying direction passes through the feed-in rollers and is detached therefrom, correction of the conveying direction by the feed-in rollers is no longer effected, and accordingly, the extent of such skew feed increases. Furthermore, the discharge rollers hardly have holding force for the sheet material, and accordingly, the function of correcting the conveying direction of the sheet material is hardly obtained.
Hence, in the conventional thermal activation device, the sheet material is inclined as described above, and thus the respective widths of the adhesive region thermally activated by the thermal activation head and the non-adhesive region which is not thermally activated are changed. Accordingly, it has been difficult to form the adhesive region having an intended width on the heat-sensitive adhesive layer of the sheet material.